Jesus forgives sins on his own authority, which his hearers recognized as something only God could do.

Watch what Jesus actually does, not just what people say about him. He does not tell people that God has forgiven them, the way a priest or prophet might announce a pardon. He forgives directly, as if the pardon is his to give. And the religious experts watching understood the implication immediately. Their objection is the tell. They knew that forgiving sins by personal authority was God’s prerogative, and they heard Jesus claim it.